This weekend Jeff and I descend to the bottom of a cold and dripping sinkhole in Ontario, Canada. It would appear that most are unaware of the existence of these pits, thinking that they only occur in Florida and other places where there have been some well publicized swallowings of people and posessions. Sinkholes occur for several reasons, but in stable rock they develop slowly and predictably over thousands of years and it is only the careless who end up lying broken and dying at their bottom.

In Toronto, it is most likely an underground pipe that has broken and eroded the lake deposited sediment beneath the city streets that would pose a sinkhole hazard. On rare occasions there have been collapse windows that have unexpectedly appeared in farmer’s fields, and of course there have been the celebrated cave-ins around mining communities like Cobalt and Kirkland Lake that have resulted in the loss of buildings. I believe it was in Timmins that a school bus was swallowed up one night with a sleeping beggar who had sheltered there, little suspecting that he would wake up entombed within the earth.

I spend my weekends caving and it appears that for the scarcity of horizontal cave openings near Toronto, it is now the vertical shafts that we are breaking open in hopes of exposing buried tunnels. Pictured here is one such shaft that sinks deep into virgin rock.

Greetings cavers and cave interested readers. As you might have gathered by the photo, I have spent some time underground today in the solitary and yet thought provoking pursuit of extreme cave digging. Admittedly there were times when it felt like I was buried alive and there were also the issues of trying to squeeze back out of the hole by which I had entered this tunnel.

JC and I have delayed a return to the shafts that we found last weekend (so as not to bother the land owner too much) and instead we investigated another lead. Somewhere near that lead we found a blind valley and in clearing the sticks and leaves away we found a pheratic tube that is choked with yellow clay.

As I was digging there was plenty of time for reflection and I came up with the thought that this tube must have drained the lake that we think must have existed in the hollow of a nearby field. Although the field is in an area of highly developed karst, it’s contact with the rock is sealed by this clay and so not surprisingly the drainage points are limited to a few locations – this is one of them. again, this geographic situation is similar to the geography of the cave system that we found in Hamilton last year – Wasteland Waterway (Consider this when looking for caves in Ontario).

We are still unsure of when the cave tunnels were choked (glacial or at the initial clearance of the land), but it must have been some time ago as calcite has dripped down onto the surface of the fill and formed a solid scab in places. Obviously our excavations have to be very carefully performed as we do not want to damage speleothems. The tube appears to be elliptical in shape and the formations fill the airspace between the clay choke and the roof. whatever we excavate will be our crawlspace.

It seems that the cave geography repeats itself. To a farmer it is a curse but to me this sinkhole is very much like the Blue Barrel Sink and as you might already be aware, there is cave tunnel beneath Blue Barrel sink. and again, just like blue Barrel sink there is the surface depression that connects to the nearest sinkhole in the patch of trees in the distance.

Ontario’s karst geography is screaming “CAVE” and so few can hear the noise. Put your ear down in the bottom of this sink at springtime, when the snow is melting and if you can hear the same roar that JC and I heard from the river beneath Blue Barrel, well then you know to dig and you’ll open up a cave. This whole are is pocked with sinkholes, but most are taking surface streams.

This steep sided cone-shaped sinkhole seems indicative of soil being eroded from beneath. If you are searching for caves in Ontario, this is a very good indicator that there is a tunnel below. I think that those larger tear drop sinks that take small streams are seldom home to larger tunnels, but where the tunnels all meet up underground in a single trunk passage, that is the real prize. Without apparent surface flow, these dimples in the field are likely to be your most profitable use of time – they are eating soil because there is water flowing beneath.

Usually in seeing a sinkhole it suggests that the surface is being nibbled away from beneath. Not surprisingly there are tunnels under this farmer’s field. At the bottom of this sinkhole there is a barrel in the hole.

This feature beside which JC is standing sits about 50 meters from our newly discovered cave – Wasteland Waterway. All along the front of this buried ridge – not easily seen from a distance there are numerous sinkholes, several of which are taking streams from a marshy area nearby. On second thought, it might also be a buried fissure, it’s hard to tell as there is so much overburden.

JC and I are still trying to understand the local geology. We are optimistic that the cave we have found connects several of these sinks.

In about two or three weeks we are returning to follow the passage for a greater distance. We think we are on to something that could be substantial if it doesn’t sump. Then again XS Wire also looked a bit like this (but smaller) and it sumped pretty quick.

Seeing that the tunnel beyond where we had crawled begins meandering it might suggest a lot of open bedding plane space. The layer in which the passage has formed is very much pitted and corroded, the layer above the tunnel seems to erode much more smoothly. There is evidence of flooding up beyond the tunnel entrance so I’d imagine that this is not the place to be on a rainy day.

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Following the release some time ago of my book "Rockwatching; Adventures above and below Ontario", I am pleased to announce the release of my new book "Tamarindo; Crooked Times in Costa Rica". It is a story of opportunity. Edgehill Press is the publisher. (www.edgehillpress.com)